It is known to provide, in the production of glass panes, plates or sheets (hereinafter referred to generally as "panes") a roller conveyor or grate which can transport a glass pane through a treatment station. For example, when the glass panes have been heated previously or are in a heated state after an earlier operation, the hot glass panes can be carried by such a conveyor through a controlled/cooling station or some other treatment station conventional in the Art. Alternatively, or in addition, the glass pane can be heated on the conveyor, e.g. in a heat treatment oven, furnace or kiln.
Since the heating of glass tends to soften it, there is always the danger that the transport of heated glass panes and roller conveyors, traveling grates or the like may result in some sag of the glass between the support locations.
Thus, it is known to provide arrangements for minimizing this sag. For example, in German Patent No. 740,219 (FIG. 1 and page 2, lines 32 through 58), the glass panes are fed through the treatment station or stations with a unidirectional translation velocity component of the glass corresponding to the transport velocity, and within the treatment station are given a back-and-forth motion by angular oscillation of the support rollers. The treatment is carried out while the panes are moved in this manner.
When treatment is terminated, the translatory component is imparted to the glass panes by displacement of the rollers after the oscillating or back-and-forth movement is terminated.
While the back-and-forth or oscillating movements promote treatment and minimize sag during the treatment, there is always a danger of sag as the glass panes are transported after the treatment. Furthermore, since the forward travel of the glass panes is not continuous during the treatment the movement of the glass panes through the treatment station or stations is intermittent with interruption in transport within the treatment stations while the oscillations are imparted to the glass panes.
These complex movements require a complicated glass displacement apparatus, do not eliminate the danger of sag at all points at which a heated glass pane is supported by the conveyor, and contributes to limiting the capacity of the plant to process the glass panes. These problems are especially pronounced (particularly with respect to the danger of sag) when extremely high temperatures are utilized as part of the treatment, i.e. where the glass is supported within an oven or furnace.
It is also known to avoid the sagging problem for continuously displacing the glass panes through the treatment station by operating the conveyor at extremely high speeds, whether continuously, in steps or with interruptions. In such systems the danger of sag remains as the speed is reduced and hence the speed must be maintained at such a high level that treatment stations are prohibitively long for a given residence time. The cost of such apparatus is also prohibitive.